Conventionally, there has been known an assembled battery in which a plurality of cells are accommodated in an assembled battery case (see JP-A-11-329517). The assembled battery is mounted on an electric vehicle or a hybrid vehicle (hereinafter simply referred to as “vehicle”), for example. As shown in FIG. 8, the assembled battery includes: a plurality of modules 102 in each of which a plurality of cells 101 are connected to each other in series and/or in parallel to each other; a plurality of module cases 103 in each of which each module 102 is accommodated; and an assembled battery case 104 in which all module cases 103 are accommodated. The assembled battery 100 includes a cell cooling fan 105. The assembled battery 100 also includes: a duct 106 through which outside air is supplied to the inside of the module case 103 from the outside of the assembled battery case 104; and a duct 107 through which air used for cooling the cells 101 in the module case 103 is discharged to the outside of the assembled battery case 104. The ducts 106, 107 are disposed in the inside of the assembled battery case.
In this assembled battery 100, outside air is supplied to the inside of the module case 103 through the duct 106 having the cell cooling fan 105 and, after outside air flows through the module case 103 while being brought into contact with the cells 101, outside air is discharged to the outside of the assembled battery case 104 through the duct 107. With such an operation, the cells 101 are cooled.
When an ambient temperature around a vehicle (outside temperature) is high so that an inner temperature of the assembled battery case 104 is increased, the cooling efficiency may be lowered. That is, due to the increase of the inner temperature of the assembled battery case 104, a temperature of outside air which flows through the duct 106 disposed in the inside of the assembled battery case 104 (to be more specific, the duct 106 through which outside air is supplied to the inside of the module case 103) may be increased by being influenced by the inner temperature.